DATABASE C:\Program Files\USGS\Phreeqc Interactive 2.6\wateq4f.dat
#
#   Remove Mg and Ca sorption
#
SURFACE_SPECIES
Hfo_wOH + Mg+2 = Hfo_wOMg+ + H+
    log_k     -15
Ca+2 + Hfo_wOH = Hfo_wOCa+ + H+
    log_k     -15
#
#   Define brine
#
SOLUTION_SPREAD											
 -units mol/kgw											
 Description	 Number	Temp	    pH	         pe	     Ca	     Mg	    Na	     Cl	       C	        S	       As
            	      		      	 O2(g) -0.7	       	       	      	 charge	        	         	 uMol/kgw
       brine	 1	25	5.713	4	0.4655	0.1609	5.402	6.642	0.00396	0.004725	0.05
#
# Define equilibrium_phases 1-10
#
EQUILIBRIUM_PHASES 1-10
        Dolomite        0.0     1.6
        Calcite         0.0     0.1
END
#
# Equilibrate brine with calcite and dolomite
# Save solutions 1-10
#
USE solution 1
USE equilibrium_phases 1
SAVE solution 1-10
END
#
#   Define initial exchange and surface 1-10
#
TITLE Initial exchange and surface
EXCHANGE 1-10
    X       1
    -equilibrate with solution 1
SURFACE 1-10
    -equilibrate with solution 1
    Hfo_w   0.07   600    30
END
#
#   Define 20xRainwater
#
SOLUTION_SPREAD											
 -units mmol/kgw											
 Description	 Number	Temp	    pH	         pe	     Ca	     Mg	    Na	     Cl	       C	        S	
            	      		      	 O2(g) -0.7	       	       	      		        	 charge	
20xRainwater	0	25	4.6	4	0.192	0.036	0.123	0.134	0.011	0.235	
#
# Equilibrate rainwater with calcite, dolomite, CO2
# Save as solution 0
#
EQUILIBRIUM_PHASES 0
        Dolomite        0.0     1.6
        Calcite         0.0     0.1
        CO2(g)          -1.5    10.
SAVE solution 0
END
#
#   Advect reacted rainwater through column
#   5 shifts
#
SELECTED_OUTPUT
	-reset false
	-file ok.sel
	-solution
	-pH
	-tot   Cl	Na Ca As
	-mol	Hfo_wOH2+ NaX CaX2 MgX2 
	-eq	Calcite Dolomite
USER_PUNCH
-headings As(ug/L)
-start
10 PUNCH TOT("As")*1e6*74.92
-end
ADVECTION
    -cells 10
    -shifts 1
    -punch_frequency 5
    -warnings true
END